The present invention relates to medical diagnostic imaging and in particular to a method and system for enhancing three-dimensional images.
In the medical field, it is common to use ultrasound diagnostic equipment to view internal organs of a subject. For example, in diagnosing Prostate cancer, a diagnostician uses transrectal ultrasound (TRUS) to identify whether lesions are present as well as to determine the location, size and extent of lesions if present. Conventional ultrasound diagnostic equipment typically comprise an ultrasound probe for transmitting ultrasound signals into the subject and receiving reflected ultrasound signals therefrom. The reflected ultrasound signals received by the ultrasound probe are processed and a two-dimensional image of the target under examination is formed.
Unfortunately, this conventional equipment produces two-dimensional images even though the target under examination is three-dimensional. Also, the two dimensional images represent a single thin plane taken at an arbitrary angle to the target making it very difficult to localize the image plane in the target and very difficult to reproduce an image at a particular location at a later time. Furthermore, the imaged plane is usually not a clear detailed image but rather a series of shaded shapes which requires a considerable level of skill to interpret.
In U.S. application Ser. No. 08/419,049 and U.S. Pat. No. 5,454,371, assigned to the assignee of the present application, the contents of which are incorporated herein by reference, three-dimensional ultrasound imaging systems are described. Although, these systems overcome disadvantages associated with the prior art, improvements to enhance imaging and to increase the speed by which three-dimensional images can be generated from two-dimensional ultrasound images are continually being sought.
It is therefore an object of the present invention to provide a novel system and method for generating a three-dimensional image from a succession of two-dimensional images, a novel image processing means for enhancing the three-dimensional image viewed by a user and, a novel ultrasound imaging system.
According to one aspect of the present invention there is provided a three-dimensional imaging system for acquiring a succession of two-dimensional images of a target volume represented by an array of pixels I(x,y,z) into a three-dimensional image represented by a volumetric image array V(x,y,z) comprising:
scanning means to scan said target volume along a predetermined geometric scanning path and generate a succession of digitized two-dimensional images thereof representing cross-sections of said target volume on a plurality of planes spaced along said scanning path;
memory storing said succession of digitized two-dimensional images together with other related image data defining the location of said two-dimensional images in said memory and defining interpretation information relating to the relative position of pixels within said two-dimensional images and to the relative position of pixels in adjacent two-dimensional images within said target volume;
transformation means receiving said digitized two-dimensional images and said other related image data and transforming said two-dimensional images and said other related image data into a volumetric image array;
display means to generate a three-dimensional image of said target volume from said volumetric image away; and,
an image processing means for processing said three-dimensional image of said target volume to render an enhanced three-dimensional image.
Preferably, the image processing means includes user changeable image processing parameters.
Also preferably, the image processing means includes user selectable image processing parameters.
Also preferably the changeable image processing parameters include modifying a ray depth.
Also preferably, the selectable image processing parameters include selecting from a plurality of image processing techniques.
Also preferably the image processing techniques include, but are not limited to, Texture Mapping, Maximum Intensity Projection (MIP), Conditional MIP (CMIP) and/or Ray Summation (Raysum).
Also preferably, the user selectable and user changeable image processing parameters are selected and changed via a user interface.
Also preferably, the user interface is a graphical user interface.
In one embodiment, a depth-limited image processing means is employed whereby, from a model representing at least a portion of the three-dimensional volumetric array, a user selects a ray-depth from at least one face of the model thereby forming a xe2x80x9cthick-planexe2x80x9d region of interest. All voxels within the xe2x80x9cthick-planexe2x80x9d are processed successively according to a user selected imaging technique along the depth of the ray, the results of which are projected onto corresponding screen pixels to produce an enhanced three-dimensional image.
In another embodiment, an adaptive depth-limited image processing means is employed whereby , from a model representing at least a portion of the three-dimensional volumetric array, a user selects a ray-depth from at least one face of the model. In combination with the ray depth, a user specified condition is selected with which voxels are examined. Voxels within the model interior are first processed according to the user specified condition. Voxels meeting the user specified condition are then processed by a user selected imaging technique, the results of which are projected onto corresponding screen pixels to produce an enhanced three-dimensional image. All other voxels are ignored thereby increasing processing speed.
The ray-depth thereby limits the processing depth within the volumetric array and therefore limits the number of voxels processed to produce the enhanced three-dimensional image. Processing the reduced number of voxels results in quick processing speeds which permits at or near real-time enhanced three-dimensional image updating. Accordingly, this further permits the user to view enhanced three-dimensional images as the model is manipulated (rotated, translated etc.) via a user input device and graphical user interface.
The user selected imaging technique may include, but is not limited to, Texture Mapping, Maximum Intensity Projection (MIP), Conditional MIP (CMIP) and/or Ray Summation (Raysum).